Method of producing seamless metal tubes

ABSTRACT

SEAMLESS TUBES ARE PRODUCED, FROM HOLLOW BLANKS OBTAINED BY CONTINUOUSLY CASTING, AND THE BLANKS HAVE A RATIO OF OUTER TO INNER DIAMETER OF ABOUT 2:1 TO ABOUT 5:1 AND A WALL THICKNESS OF AT LEAST 150 MM. AND AN INNER DIAMETER OF AT LEAST 80 MM., BY STRETCH ROLLING THE BLANKS, HEATING THEM AND FURTHER ROLLING THEM. A ROLLING MACHINE INCLUDES A THREE-RTOLL DIAGONAL ROLLING MILL, AND EACH ROLL HAS A SHOULDER CALIBRATION, AND A HOLLOW NOZZLE CARRYING MANDREL ROD THAT IS CAPABLE OF RECEIVING AND SPRAYING A PRESSURE WATER.

June 1, 1971 u. PETERSEN ETAL 3,581,384

METHOD OF PRODUCING SEAMLES S METAL TUBES Filed June 25, 1968 6 Sheets-Sheet 1 Jnrenlora Ulrich rater-eon, rricdrit/i fi ms Gretna/in and Jon jeve U. PETERSEN ET AL METHOD OF PRODUCING SEAMLESS METAL TUBES June 1, 1971 6 Sheets-Sheet 2 Filed June 25, 1968 @I l i IUD Jnrenfons: arid Pd'epgw June 1, 1971 u, 5 ETAL METHOD OF PRODUCING SEAMLESS METAL TUBES 6 Sheets-Sheat 5 Filed June 25, 1968 June 1971 u. PETERSEN ErAL METHOD OF PRODUCING SEAMLESS METAL TUBES 6 Sheets-Sheet 4 Filed June 25, 1968 a n w m M m l S. ewmm MW; 4% jmuw m 1 M wlm ml 3 W June 1, 1971 u, PETERSEN EI'AL 3,581,384

METHOD OF PRODUCING SEAMLESS METAL TUBES Filed June 25, 1968 6 Sheets-Sheet 5 bran/ans.- Ulr c Waters, fi'vkdn fine G r n om! Jul yank,

June 1, 1971 PETERSEN EI'AL 3,581,384

METHOD OF PRODUCING SEAMLESS METAL TUBES Filed June 25, 1968 6 Sheets-Sheet 6 Jnrentara:

87 flMA a km- United States Patent 3,581,384 METHOD OF PRODUCING SEAMLESS METAL TUBES Ulrich Petersen, Dusseldorf, and Friedrich-Hans Grandln and Jos Severin, Mulheim (Ruhr), Germany, assignors to Manuesmann A.G., Dusseldorf, Germany Filed June 25, 1968, Ser. No. 742,475 Claims priority, application Germany, June 28, 1967,

P 15 58 276.0; Mar. 30, 1968, P 17 52 078.4; Apr.

Int. Cl. B23k 19/00; 1323 17/00, 25/00 U.S. Cl. 29--527.7 7 Claims ABSTRACT OF THE DISCLOSURE Seamless tubes are produced, from hollow blanks obtained by continuous casting, and the blanks have a ratio of outer to inner diameter of about 2:1 to about 5:1 and a wall thickness of at least 150 mm. and an inner diameter of at least 80 mm., by stretch rolling the blanks, heating them and further rolling them. A rolling machine includes a three-roll diagonal rolling mill, and each roll has a shoulder calibration, and a hollow nozzle carrying mandrel rod that is capable of receiving and spraying a pressure water.

The invention relates to seamless metal tubes, and relates more particularly to methods of and to machines for producing such tubes.

Methods and machines are known today to produce seamless metal tubes; they are, however, deficient therein in that they do not permit an economically eflicient production of seamless tubes. Furthermore, present methods and machines are deficient therein that for maintaining certain required qualities in the production, they have led to the adoption of expensive steps.

It is accordingly among the principal objects of the invention to provide for the efficient production of highquality seamless metal tubes without the aforesaid drawbacks of the prior art.

Further objects and advantages of the invention will be set forth in part in the following specification and in part will be obvious therefrom without being specifically referred to, the same being realized and attained as pointed out in the claims hereof.

Broadly speaking, the instant invention provides for the rolling of hollow blanks obtained by continuous casting; the hollow blanks have a ratio of outer diameter to inner diameter of from about 2:1 to about 5:1 and have a wall thickness of at least 150 mm. and an inner diameter of at least 80 mm. The length of the hollow blank is suitable and such that greater lengths of seamless tubes can be produced with the subsequent rolling operation than is possible by rolling hollow blanks which had been obtained either by pressing or by rolling or by diagonal rolling.

In accordance with one embodiment, the instant invention provides for a controlled cooling of the inner and/ or outer surfaces of the hollow blank during the continuous cast, so as to place the line of segregation into a region of cross section of the wall which is spaced from the external or internal wall surface for at least one-fourth of said wall thickness.

In accordance with a further feature of the instant invention, the line of segregation within the aforesaid region is placed as far inwardly as possible if the subsequent forming of the hollow blank or casting section primarily applies to the exterior zone of the cross section and, conversely, is placed as far outside as possible if the subsequent forming is primarily applied to the inner zones of the cross section.

The instant invention also provides for a descaling of 3,581,334 Patented June 1, 1971 the internal surface of the hollow blank after the continuous casting and prior to the subsequent forming; and the descaling may be accomplished by directing steam or pressure water to the still hot inner surface.

The descaling may, however, also be carried out during the first forming operation performed on the hollow blank, namely by the forming itself, thus, by means of the forming means themselves.

For the forming after the continuous casting, various possibilities apply. In accordance with one embodiment of the invention, the hollow blank is formed by means of diagonal rolls over an inner tool, such as a mandrel or mandrel rod, by means of a diagonal rolling mill that has three or more rolls.

In accordance with another embodiment, the aforesaid forming, such as stretch rolling may be carried out in several thrusts, for instance after a severing and following a subsequent heating or a re-heating of the intermediate product; and the forming may be carried out during the second thrust by the inner tool, or, if desired, during subsequent thrusts with or without the internal tool be continued in successive rolling frames, or in reversing operation, in one or in several rolling frames.

In accordance with a preferrel embodiment, the first stretch rolling results either in a retention of the original internal diameter of the hollow blank, or in but a slight increase of that internal diameter, or in a reduction thereof.

The following examples of the rolling after the continuous casting are given below:

(a) The hollow blank, after a stretch rolling and heating, in succession is subjected to a diagonal rolling and a reciprocating rolling process (also known as Mannesmann process) and thereafter, perhaps following a severing and a heating, is expanded by diagonal rolling over a conical flaring mandrel and, after that expansion, is subjected to a sizing rolling operation.

(b) The hollow blank may, however, after the stretch rolling and heating subsequently be subjected to a diagonal rolling and a plug mill rolling operation, which is followed by reeling, heating and sizing rolling. For this method there may be used a tensile stressed stopper rod that carries a mandrel plug.

(c) A further combination provides that the hollow blank after a stretch rolling and heating, is subjected in succession to a diagonal rolling, a collision operation, or a combined collision and drawing operation, which is followed by reeling, heating and stretch reduction rolling.

(d) A further combination provides in accordance with a modification, that the hollow blank after the stretch rolling and re-heating, is subjected, in succession, to a diagonal rolling, a continuous rolling over a mandrel rod, a heating and a stretch reduction operation.

The hollow blank which has been obtained by continuous casting, or by other means, may be stretch rolled, by means of three diagonal rolls over a follower mandrel rod the length of which is attuned to the length of the finished tube, to a tubular bloom; and the tubular bloom will immediately subsequently, after the diagonal rolling, be rolled into the tube continuously on the mandrel rod that has remained on the interior of the tubular bloom. The mandrel rod is inserted into the hollow blank before the diagonal rolling; and during the insertion of the mandrel rod into the hollow blank, the scale on the interior of the hollow blank may be removed by spraying with pressure water.

In accordance with a preferred embodiment, the instant invention provides that the tubular bloom together with the mandrel rod disposed on the interior thereof, is subjected prior to the continuous rolling to an intermediate heating, preferably an inductive heating.

In accordance with a further feature of the invention, the product emerging from the rolling mill is stretch reduced either warm or cold, and either with or without any internal tool, and that during the forming of the tube by stretch reducing without internal tool following the continuous rolling over a mandrel rod, there will follow a disconnecting rolling with or without rotation of the tube.

A machine for the method described under ((1), above, comprises a three-roll diagonal rolling mill, and each of the three rolls is provided with a shoulder calibration. The mandrel rod is hollow and has spray nozzles near its forward end, and is rearwardly connected to a feed water conduit for a pressure fluid, such as pressure water, and that conduit is automatically disconnectable from the mandrel rod.

(e) Furthermore, a further feature may be provided for producing seamless tubes with a diameter larger than 800 mm. and a Wall thickness larger than 15 mm.; in accordance with which the hollow blank is first rolled, by means of drum rolls, to an external diameter which is slightly larger than the final diameter of the finished seamless tube, and is rolled to a Wall thickness which is larger than the wall thickness of the finished tube; and subsequently, the hollow blank is stretch rolled by means of diagonal rolling that proceeds simultaneously inwardly and outwardly of the hollow blank, and proceeds to roll the hollow blank to the final dimensions of the seamless tube, in point of external diameter and wall thickness. The diagonal rolling may proceed in accordance with several thrusts, in reversing operation.

The instant invention offers the advantage to produce in an economically efiicient manner seamless tubes with a diameter in excess of 800 mm. and a wall thickness larger than 15 mm., and to utilize the well-known technical advantages of seamless tubes as compared to Welded tubes; this applies also to steel tubes of the aforesaid dimensions. This is of particular importance for tubes and other hollow bodies which are composed of steels that are diflicult to weld or which are maintained under very high internal pressures.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a pictorial schematic representation of a series of steps in accordance with the instant invention;

FIG. 2 is a pictorial schematic representation of a heating step following the steps of FIG. 1, and followed by a series of steps in accordance with an embodiment of the invention;

FIGS. 3-5 are pictorial schematic representations similar to FIG. 2, but embodying modifications;

FIGS. 6-11 are schematic views, partly in section, indicating various process steps of the method of FIG.

FIG. 12 is a fragmentary elevational view, partly in section, of a hollow mandrel rod with an insertion device;

FIG. 13 is a large scale elevational view, showing tongs for the automatic engagement and disengagement of the pressure water feed conduit, showing the tongs in open position;

FIG. 14 is a large scale fragmentary elevational view of the tongs of FIG. 13, but showing them in close position;

FIG. 15 is a fragmentary sectional view of a hollow blank;

FIG. 16 is a schematic elevational view of a drum rolling arrangement;

FIG. 17 is a schematic elevational view, similar to FIG. 16, but showing the position of the parts near the end of the rolling operation;

FIG. 18 is a fragmentary sectional view, similar to FIG. 15, but showing the blank after the rolling operation of FIGS. 16 and 17;

FIG. 19 is a fragmentary evelational view, partly in section, of a multiple roll diagonal rolling mill; and

FIG. 20 is a fragmentary sectional view, similar to FIGS. 15 and 18, and showing the seamless tube.

Referring to FIG. 1, there are illustrated from left to right a continuous casting machine 1 of any suitable well-known conventional construction. A flaming device 2 is positioned near thereto, and proceeding further from left to right, a saw 3 is provided for severing the casting into blanks. Before the blank is further worked upon, it will be heated in a furnace 4, and subsequently be stretch rolled by means of a three-roll diagonal rolling mill 5 that operates with an internal tool of suitable construction and in a conventional manner in order to stretch the blank without imparting thereto any oval shape. After this stretch rolling, the 'blank may again be severed into parts, with the aid of a saw 6.

During the further operation, the hollow blanks produced as shown in FIG. 1 usually are subjected to a reheating, for instance in a rotational furnace 7 (FIG. 2).

In accordance with the embodiment of FIG. 2, the hollow blank that emerges from the furnace 7 is subjected to a diagonal rolling in a diagonal rolling mill 8. The workpiece is then subjected to a reciprocating rolling process (also known as Mannesmann process) in an appropriate rolling mill 9, is then severed by a saw 10, is then heated in a heating device 11, and is then enlarged in an enlarging rolling mill 12 with flaring mandrel 13; and lastly is subjected to the action of a sizing rolling mill 14.

In the modification of FIG. 3, the action on the workpiece of the furnace 7 is followed by a diagonal rolling mill 8 that has two rolls and a mandrel. The bloom that emerges from the diagonal rolling mill 8 is thereafter subjected to plug mill rolling in an appropriate rolling mill 15, that has a tensile stressed stopper rod that carries a mandrel plug; in the rolling mill 15 the workpiece is rolled to a tube, and thereafter it is subjected to the action of a reeler 16, a heating furnace 11, and a sizing rolling mill 14.

In accordance with the modification of FIG. 4, the workpiece that emerges from the furnace 7 is subjected to the action of a stretch rolling mill 17 that has three rolls, then to the action of a push-bench 18, a reeler 16, a heating furnace 11, and a stretch reducing device 19.

In accordance with FIG. 5, the workpiece emerging from the furnace 7 is subjected to the action of a stretch rolling mill 17 with three rolls, to a Konti rolling mill 20, a heating furnace 11, and a stretch reducing device 19, in succession.

In accordance with the illustration of FIG. 6, the hollow blank 21 has thick walls and is disposed in advance of the three-roll diagonal rolling mill 17. The rolls of that rolling mill 17 have shoulder calibrations 17a, and behind the same there is arranged the Konti rolling mill 20. The mandrel rod 22 is ready to be inserted on an insertion device that includes an endless chain 23.

FIG. 7 illustrates how the hollow blank in the diagonal rolling mill 17 is rolled on the mandrel rod 22 into a tubular bloom 24.

In FIG. 8, this rolling step is completed. The bloom 24 proceeds with the mandrel rod 22 immediately following the diagonal rolling, into the Konti rolling mill 20.

FIG. 9 illustrates the continuous rolling the bloom 24 into the tube 25.

FIG. 10 illustrates how the finished tube 25 with the mandrel rod 22 is disposed behind the Konti rolling mill 20.

FIG. 11 illustrates schematically how the mandrel rod 22 is removed off the tube 25, with the aid of tongs 26. Thereafter, the mandrel rod 22 is transported back to the insertion device 23. The tube 25 may, however, alternatively, be removed off the mandrel rod 22 behind the Konti rolling mill 20, by means of a disconnecting roll mill (not shown).

In accordance with the illustration of FIG. 12, the mandrel rod 22 may be hollow; the mandrel rod 22 is disposed on the insertion device 23. The mandrel rod 22 has near its front end spray nozzles 27, and rearwardly is provided with a flange 28, and a recess 29; these serve for the removal of the mandrel 22 off the tube 25.

A lug 30 is connected to the insertion device 23, and has bores 31 as well as a sealing piston 32 that is disposed near the end of the mandrel rod 22. The pressure water is fed through the conduit connection 33. Near the end of the lug 30, there is provided tongs 34, that serves for the automatic connection and disconnection of the pressure water feed conduit 33 to the mandrel rod 22. The tongs 34 is mounted on a bolt 35. During feeding of the pressure water, the sealing piston 32 is pressed against the mandrel rod 22, so that the pressure water will pass through the hollow interior of the mandrel 22 and emerges therefrom through the nozzles 27 thereof.

On the legs of the tongs 34 there are mounted bolts 36 which press against a dog 37 during the forward movement of the mandrel rod 22. By this engagement, tongs 34 will be opened, and at the same time the pressure water feed be interrupted. The mandrel rod 22, having been disconnected from the tongs 34 will continue to travel with the hollow blank 21 to the three-roll rolling mill 17.

The tongs 34, as best shown in FIGS. 13 and 14, will near its final position be opened by means of rolls 38, which act against the power of a compression spring 39. During forward movement, however, the tongs 34 will be closed, by means of the pressure of the compression spring 39, about the flange 28 of the mandrel rod 22.

In FIGS. 15-22, there are shown the combination of machinery and steps for producing seamless tubes that have a diameter larger than 800 mm. and a wall thickness larger than 15 mm. FIG. 15 shows the hollow blank 40 obtained by continuous casting. The internal diameter of the blank 40 must be large enough so that the blank may be mounted on a drum rolling mill for further expansion. Such a drum rolling mill is shown at 41 in FIG. 16, and illustrates how the blank 40 is mounted therein. In FIG. 16, where is shown the rolling operation near its start.

In contrast thereto, in FIG. 17, the rolling operation is shown near its end. The diameter of the blank 40 has been increased and now forms the product 42, illustrated in fragmentary sectional view in FIG. 18.

Thereafter, the hollow product 42 will be mounted in a multiple diagonal rolling mill 43, as shown in FIG. 19. This rolling mill 43, comprises external rolls 44 and internal rolls 45 that are disposed opposite and cooperate with the external rolls 44. All the rolls show on both sides shoulder calibrations, so that the rolling mill may operate in reversing operation, and the hollow product 42 may be subjected to several thrusts in opposite reciprocating direction, in a single heat. In the rolling mill 43, the hollow product 42 is rolled into the final seamless tube 46; the final seamless tube is shown in fragmentary cross section in FIG. 20.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

Having thus described the invention, what we claim as new and desire to be secured by Letters Patent, is as follows:

1. In a method of producing a seamless tube, the steps comprising forming by nonrotatably continuously casting a hollow blank having a ratio of outer diameter to inner diameter of from about 2:1 to about 5:1 and having a wall thickness of at least 150 millimeters and an inner diameter of at least 80 millimeters and a suitable length, thereafter stretch rolling said blank, severing said blank, descaling the inner surface of said hollow blank after it has been continuously cast, heating and further rolling it free of oval shape.

2. In a method, as claimed in claim 1, and controlling the cooling during said continuous casting along the external and internal surfaces in such a manner that the line of segregation will be placed within a region of the cross section of the wall of the blank which is spaced from the inner and outer wall surface, the step of placing said line of segregation within said region as far inwardly as possible if during the subsequent rolling operation the forming is primarily applied to the external cross sectional zone and, conversely, placing said line of segregation as far outwardly as possible within said region if the subsequent forming pertains primarily to the inner zone of said cross section.

3. In a method, as claimed in claim 1, said descaling being carried out with the aid of steam or pressure water applied to the still hot internal surface of the hollow blank.

4. In a method, as claimed in claim 1, and descaling said hollow blank during the first forming, by the forming itself.

5. In a method, as claimed in claim 1, said stretch rolling comprising lengthening said hollow blank by means of diagonal rolling with the aid of at least three rolls, and with the aid of an internal tool.

6. In a method, as claimed in claim 5, said stretch rolling comprising a series of thrusts with or without severing and with an intermediate: heating of the intermediate product, said forming with internal tool being carried out during the second thrust and during subsequent thrusts with or without said internal tool continuously or in reversing operation.

7. In a method as claimed in claim 1, said descaling being carried out with the aid of flaming.

References Cited UNITED STATES PATENTS 441,375 11/1890 Norton et al. 164'76 1,527,729 2/1925 Dunajefi 164-270 2,002,415 5/1935 Otto 29527.7 2,306,771 12/1942 Bannister 29527.7 2,466,612 4/1949 Phillips et al 164-282X 3,357,095 12/1967 Klein 29-527.5 3,445,922 5/ 1969 Leghorn 29'-527.7Y

JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner US. Cl. X.R. 164-46, 270, 282 

